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Hubble Expansion

Hubble Expansion. The Milky Way has 200 billion stars and a large gravitational force. The Magellanic Clouds are irregular galaxies that orbit the Milky Way. There are 9 dwarf galaxies within 500,000 ly. Satellite Galaxies. Local Group. The nearest large galaxy is M31 in Andromeda.

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Hubble Expansion

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  1. Hubble Expansion

  2. The Milky Way has 200 billion stars and a large gravitational force. The Magellanic Clouds are irregular galaxies that orbit the Milky Way. There are 9 dwarf galaxies within 500,000 ly. Satellite Galaxies

  3. Local Group • The nearest large galaxy is M31 in Andromeda. • Together with satellites the Milky Way, M31, and the Triangulum Galaxy make up the Local Group. • This group is 10 million ly across with 700 billion stars.

  4. Virgo Cluster • The Virgo Cluster includes more than 2000 galaxies. • They all exert gravity on each other. • X-ray views show the collisions of gas and dust. visible x-ray

  5. Supercluster • The Local Group orbits the massive Virgo Cluster. • Many clusters make up the Virgo Supercluster.

  6. Most all galaxies are moving away from us. Not expected 100 years ago Distant galaxies move fastest Hubble found a simple relationship between distance and velocity. Hubble’s Law v = H0 d Hubble’s Law v = recessional velocity d = distance H0 = 1.5 to 3.1  10-18 per sec Hubble “constant” Hubble’s Law

  7. Galactic Luminosity • The distribution of luminosity in galaxies in a cluster is relatively consistent.

  8. An approximate analytical form is used to fit luminosities in a cluster. Density of galaxies F Range from L to L+dL Normalization F* There is a characteristic luminosity L* where the slope changes rapidly. Luminosity Fit

  9. Distant Light • Some objects in deep space are visible, small, and have large redshifts. • Hubble’s law suggests that these objects are very distant. • Some are billions of light years away. larger wavelength nearby galaxy distant object

  10. Hubble’s law suggests that the galaxies in the universe are spreading out over time. From Einstein’s general relativity this happens as space itself expands. The dimensional scale increases as the universe expands. Expanding Universe

  11. As the universe expands the wavelength of light stretches. At the burst of light, 3000 K. Peak radiation was 1 micron. This is visible light. The universe is 1000 times larger. The temperature is 3 K. The peak radiation is 1 mm. These are microwaves. Stretching Light 1 wavelength, small universe 1 wavelength, expanded universe

  12. Some distant objects were first observed as intense radio sources. They were star-sized, but too bright. They were named quasi-stellar radio sources—quasars. Quasi-Stellar Objects

  13. Distant Past • Looking at a faraway object is equivalent to looking back in time. • If a quasar is 5 billion ly away, we are seeing the universe 5 billion years ago. Andromeda — 2 million years ago Earth PKS 1127 — 4 billion years ago

  14. Energy Release • Quasars emit in all parts of the electromagnetic spectrum. • Many shine with the light of 100 galaxies. • Quasars can flare up to 10,000 times the light of a galaxy. 3C279, a quasar photographed in gamma rays

  15. Disk and Jets • Radio measurements show two giant jets of radiating gas. • Visible light and x-rays see a disk of gas, dust and stars. • The most intense radiation is from a small area at the center.

  16. Quasars form from a supermassive black hole. The black hole draws stars and dust to its center. The material is accelerated to high velocity and ejected out either side. Jet Formation

  17. Supermassive black holes are observed in most galaxies. All quasars have large redshifts. Very far away Early universe Quasars may be consistent with early galaxies. Early Galaxies

  18. Active Nuclei • Some nearby galaxies show jets of radiating gas. • AGN: Active galactic nuclei • The jets are consistent with a supermassive black hole.

  19. Visible elliptical galaxies have black holes in their center. The jets are only seen with radio telescopes. These are called radio galaxies. Radio Galaxies

  20. Galactic Evolution • Astronomers believe that large galaxies form quasars. • As the early dust is used up the quasar fades. • The galaxies are active as additional matter is consumed.

  21. The Chandra X-ray Observatory has observed two supermassive black holes in the same galaxy. The galaxy NGC 6240 is 400 million light years away. When the holes collide in a few hundred million years, the gravity waves will be felt on earth. Colliding Black Holes

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